/*
 * Copyright 2019 Immutables Authors and Contributors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.immutables.criteria.repository;

import org.immutables.criteria.expression.Collation;
import org.immutables.criteria.expression.Expression;
import org.immutables.criteria.expression.ImmutableQuery;
import org.immutables.criteria.expression.Ordering;
import org.immutables.criteria.expression.Query;
import org.immutables.criteria.matcher.Matchers;
import org.immutables.criteria.matcher.Projection;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Objects;
import java.util.stream.Collectors;

/**
 * Template class for Readers. For future API compatibility prefer extend it rather than
 * implement {@link Reader} directly.s
 */
public abstract class AbstractReader<R extends Reader<R>> implements Reader<R> {

  private final ImmutableQuery query;

  protected AbstractReader(Query query) {
    Objects.requireNonNull(query, "query");
    this.query = ImmutableQuery.copyOf(query);
  }

  protected abstract R newReader(Query query);

  /**
   * Expose current query (used mostly for SPIs)
   */
  Query query() {
    return query;
  }

  @Override
  public R orderBy(Ordering first, Ordering... rest) {
    if (!query.collations().isEmpty()) {
      throw new IllegalStateException("OrderBy was already set");
    }

    final List<Ordering> orderings = new ArrayList<>();
    orderings.add(first);
    orderings.addAll(Arrays.asList(rest));

    final List<Collation> collations = orderings.stream().map(x -> (Collation) x).collect(Collectors.toList());
    return newReader(query.addCollations(collations));
  }

  @Override
  public R groupBy(Projection<?> first, Projection<?> ... rest) {
    if (!query.groupBy().isEmpty()) {
      throw new IllegalStateException("GroupBy was already set");
    }

    final List<Projection<?>> all = new ArrayList<>();
    all.add(first);
    all.addAll(Arrays.asList(rest));

    final List<Expression> groupBy = all.stream().map(Matchers::toExpression).collect(Collectors.toList());
    return newReader(query.addGroupBy(groupBy));
  }

}
